fix: adds David implementation of Junit Tests for Employee class and EmployeeManager

Author: Dadenaike251

lesson_15/tdd/tdd_app/src/main/java/com/codedifferently/lesson15/Employee.java

@@ -57,4 +57,4 @@ public String getDetails() {
         + salary;
   }
 }
-// dd
+// dd

lesson_15/tdd/tdd_app/src/test/java/com/codedifferently/lesson15/EmployeeManagerTest.java

@@ -90,7 +90,7 @@ public void test_getEmployeeCount() {
 
     // Act
     int count = employeeManager.getEmployeeCount();
-ß
+
     // Assert
     assertEquals(2, count);
   }